During a posterior spinal fixation procedure a plurality of metal rods may be connected by the surgeon to the spinal column of a patient by a series of open back hooks or other spinal fixation devices. The rods are connected to the open back hooks and follow the curvature of the patient's spine. An example of an open back hook may be had by reference to U.S. Pat. Nos. 4,269,178 and 4,815,453, although such hooks are not limited thereto. An open back spinal hook may be any suitable spinal hook having a slot-type opening into the body of the hook, enabling an elongated spinal rod to pass through the slot for seating arrangement with the hook. The subject matter of the referenced patent numbers is provided solely to provide an understanding of the environment for the invention and in no way should be considered limiting.
Generally the rods are inserted into the open back hooks by applying pressure to the rod using a rod pusher as illustrated in U.S. Pat. No. 4,927,425. However, it is not uncommon for additional force or stability to be required to seat the rod within the open back hook. In such cases, a surgeon attaches a clamp to the hook and uses a mechanical device, such as the rod pusher, to seat the rod.
It is considered most convenient if the clamp and rod pusher or introducer are interconnected. An example of such a combination hook clamp and rod introducer is manufactured by Stuart, Inc. of Greensburg, Pa. and sold under the designations 84609 Bulb hook holder and 84607 rod introducer. In the Stuart device the rod introducer includes a partially threaded screw shaft having a swivel head connected at one end for contacting the rod and a wing nut connected at its opposite end. When connected to the bulb hook holder, the screw shaft with the swivel head attached is laterally spaced from the jaws of the holder. As the screw shaft of the rod introducer is rotated, the head pushes the rod into the hook stabilized by the clamp or holder. In use, the offset orientation of the swivel head relative to the jaw causes a moment arm to be established as the spinal rod is seated into the hook. Further, even after connection of the introducer to the holder, the introducer may be rotatable about a lateral axis of the shaft relative to the holder. The rotation about the lateral axis of the shaft in combination with the offset screw shaft presents an awkward tool for the surgeon.